Two Wrongs Make a Right is a fallacy in which a person "justifies" an action against a person by asserting that the person would do the same thing to him/her, when the action is not
necessary to prevent B from doing X to A. This fallacy has the following pattern of "reasoning":

It is claimed that person B would do X to person A.

It is acceptable for person A to do X to person B (when A’s doing X to B is not necessary to prevent B from doing X to A).

This sort of "reasoning" is fallacious because an action that is wrong is wrong even if another person would also do it.

It should be noted that it can be the case that it is not wrong for A to do X to B if X is done to prevent B from doing X to A or if X is done in justified retribution. For example, if Sally is running in the park and Biff tries to attack her, Sally would eb jsutified in attacking Biff to defend herself. As another example, if country A is planning to invade country B in order to enslave the people, then country B would be justified in launching a pre-emptive strike to prevent the invasion.